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burned the rotor cap why?


Guest grunt0311

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Guest grunt0311

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I was driving down the road maybe a few small zips of speed nothing to serious I hit 6500 maybe a little more and all of a sudden I start to lose power, turn off lights, radio helps a little then nothing. The car is a 71 240 with su's and electronic ignition. I pull over and look at the engine. The center of the rotor cap has been burned, I mean the top half of the hooter where the coil wire goes to is powder and half the coil wire boot is burned off. Needless to say I didn't get it running again. I just bought this thing a couple of weeks ago, it ran ok when warmed up but backfired while cold. I also recently put the internals from a 280 tach into my 240 tach and replaced. Any ideas what my problem is?

 

Any help would be appreciated,

thanks,

 

grunt 0311

71 240

76 never got it running

 

I posted on the ignition forum please forgive me for posting here but I had no response their.

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I'll give this a try. I'm no Z expert but I have heard that the problem you are having can be caused by having the wrong ballast resistor or none at all with your coil. This in turn creates a spark that is way too hot and ends up burning the rotor :evil: . Maybe the previous owner installed a new coil and bypased the ballast upon installation. rotor caps are fairly chep. Good luck.

 

I think I am at least partially right on this one.

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My guess is the coil wire to cap connection just got corroded causing the electronics box to kick up the juice to overcome the extra resistance. The white powder is most likely aluminum oxide (the aluminum equivalent of rust) which doesn't conduct. The cap may have been cracked in places causing cross fires (backfires when cold) adding to the problem.

 

I would just do an ignition tune up (plugs, wires, obviously cap and rotor). Make sure to use the dieelectric grease when connecting the plug wires (it helps prevent oxidation). Check and clean all the contacts (including the power wires to the coils) and check the coil insulator very carefully for any type of hairline cracks. Beyond that just watch it carefully and see if any problems reoccur.

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Guest grunt0311

D,

 

No I haven't left yet, but you never know when in this gun club. All my guys are already there. It's going to happen soon. Thanks for all the help all I will check for cracks and try and figure out what a ballast thing is. I could use a little proffesional help on the carbs though...ANYONE?

 

john

grunt0311

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If you have an electronic ignition, the ballast resistor might very well be bypassed. The ballast resistor only keeps the points from being fried with excess current. If your electronic conversion replaced the points, then the ballast resistor is almost certainly bypassed or removed. My electronic ignition conversion kept the points, but still had me bypass the ballast resistor since the coil current was being supplied by the box, not points.

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Guest grunt0311

well I replaced the rotor cap and rotor. I figure it was that the coil wire wasn't tight and it arched. But now that I have replaced those things and checked the plugs it won't start. I checked the plugs are getting spark...It just turns over not a hint of starting...anybody?

 

john

grunt0311

71 240

:(

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You swapped the plug wires onto the new cap one at a time, right? Make sure the firing order is good and that you haven't moved the wires over one spot. Your timing should not have changed so that shouldn't be an issue. I would really recommend replacing your plug wires too.

 

When you say spark, how hot? With an electronics box the spark should be able to jump a 1 to 2 inch gap.

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It's also very possible that the plugs could have fouled while the cap was in its death throes...

 

If this happened, the only option is to burn the carbon off of the plugs thoroughly with a propane torch, or just replace the plugs. Carb cleaner and the like won't touch that stuff.

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Guest grunt0311

:( Pulled the plugs they looked good. just a little white haze on them. I guess I will break out a book and make sure I didn't mess up the firing order. Then check the fuel. About a good place to take this thing in southern CA? Z shops? Can anyone recomend a good one I might just spend a little money on it...to make it go faster of course! :D

 

Hey Ian, I think you stole those turbo axles from me. I just saw some go on ebay for 102.50 I might just have to get you to give me a ride in that 240 again to make us even. :-D

john

grunt0311

71 240z

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